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    <title>Document</title>
</head>
<body>
    <script>
        
        function jisuan() {
        var a = +prompt('请输入第一个数字')
        var b = prompt('请输入该如何算数')
        var c = +prompt('请输入第二个数字')
        
        if (b==='+') {
            alert(a+c)
        }else if (b === '-') {
            alert(a-c)
        }else if (b === '*') {
            alert(a*c)
        }else if (b === '/') {
            alert(a/c)
        }
        }
        jisuan()
    </script>
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